Smoking Engine - Any thoughts?

[Steve Brown]

I know I said this before, but did you look for cracks in the piston at the bottom of the ring grooves? i.e. hidden by the rings when fitted. I see you are going to try other pistons so that would prove or disprove the theory. Maybe after your holiday the answer will be staring you in the face! Hope so anyway.

[harrymuffin]

Check that the piston rings have no up and down(side) play in the groove. If the rings are too loose (> 0.005") then they flutter and hence act as pumps. Ring gaps are not that important and can be up to 0.015" without detriment and can wear to that amount in normal usage. Do not use a synthetic oil until you have completed at least 500 miles as the rings will never bed in, as a lot of VW and BMW owners find to their cost. If you have the pistons out, then knife edge the inner face of the skirts which will then act as oil scrapers.

[moriniboy23]

The sideplay has been checked against the Manual specs and is/are like new

[moriniboy23]

Hi Steve, I did have a look with the rings off, and there's nothing obviously wrong with the piston from the bike.

['It must be a .....']

Hi, measured the rocker covers from a 350 Dart & 501 Coguaro which are identical and from a 500 Sport & 350 Kanguro, again identical.
On all the above rocker covers the crows feet are the same position, plus the breathers are the same dimensions.
Therefore you can mix and match the 350/500/501 covers as you please.
Have fun, Ian

[norbert]

The rocker boxes are all the same, inside. The difences are: The 501 boxes are lower (the very first 350 as well ) This his helpful with a 501 in a 350-frame. The other diference ist that the 501 boxes hava a "bore" (my vocabulary isn´t the best) on the outtake site for better cooling and the way of conecting the tube for the ventilacion is diferent. But you can certainly use the box you like.
Since more than 50 000 km with a 501 in a 350 frame I use a normal ventilacion tube for the motor with one labyrinth (I think it is enough) like on the 350ies.

One maybe useful advice: You can get the cilinderheads of (out of a 350-frame) without taking the engine of: Take of all the bolts that fix the motor, only leaving the bottom one at the rear. That way you can incline the motor and take the rear head of If you take of one of the stud bolts, I imagine you can as well get the cilinder of (never tried it because I dont like to turn them out and in if it is not really necesary.

The cracks between the esats of the valves: I have never seen a 500 o 501 head with more than 50 000 km without this cracks, they all have them, althoug their riders don´t know. Normaly you can do some tenthousands of miles without any problem with this cracks. By the time the material is coming up an one bad day the seat or fall out or is been pusched inside time by time. In the last case you will be adviced because the valve gap of 0.1 is disapearing in shorter getting intervals.
You didn´t tell us how the sparkplug looks like.

I also wonder a bit that you did deglaze the barrels. As far as I know you cannot hone a nikasil cylinder (don´t know exactly what means deglaze ). When I had to open my 501 because of a destroyed lefthand bearing of the crankshaft I noticed that the barrels after more than 60000km were in perfect condicion whithout any wear, not at the top not at the bottom. I only changed the rings.
I supose that you have controled the sealing. Sometimes some oil comes up teh stud bolts of the cilinders.

Very misteric your problem. Hope you will find out the reason of all that smoke. Are you smoking the right stuff

good luck!!!

norbert from Lübeck

[norbert]

Her you have the three types of rocker boxes

on the left the old ones, in the middel thee usual ones and on the right 501

44_IM000779_2[1].jpg (19.49 KiB) Viewed 24220 times

now on the left first series, in the middle 501, on the right the normal ones

44_IM000780_2[1].jpg (19.69 KiB) Viewed 24220 times

baue.jpg (192.83 KiB) Viewed 24220 times

norbert

['It must be a .....']

Hi, the later rocker covers (with the banjo type breather outlet) although having the same crows feet spacing they also have additional cooling fins on the inside.
Can't comment on the very early rocker covers: but aesthectically they look better?
Ian

[corsaro chris]

Love the cartoon - that'd look good on a T shirt...

Is it possible to have a copy / copyright permission?

Chris

[Ming]

You'd need to look here I think.
http://www.joebarteam.ventsdouest.com

[moriniboy23]

Well have just come in from the garage. After trying a different barrel, matched piston and new rings to no difference, the next thing was suggested to me by Chris Meyhew at NLM (thanks Chris!) - swap the carbs over, it could be fuel washing the oil off the bores.

I took the carbs off, and just thought Id check the float heights - not sure if Id ever looked at them. The front one was at 20mm instead of 23/24mm. Adjusted that, swapped them over anyway, and eureka, the smoking seems to have gone and the fluffy running that I took to be plug oiling

The weird thing is though, the wrong float height was on the front cylinder which, always seemed to be the 'good' one from the lack of smoking from that side's silencer, so whether somehow oil-smoke can migrate from the front pipe, through the balance pipe and cross-over into the opposite silencer? very mysterious but Im not going to look a gift-horse in the mouth....

[3potjohn]

Maybe the stronger cylinder was pushing the smoke into the weaker side via the balance pipe? Glad you sorted it.

[norbert]

You'd need to look here I think.
http://www.joebarteam.ventsdouest.com

No, it´s not from the Joebarteam!
It is from another artist "Holger Aue", a german cartoonist. Normaly I see him once a year. A few years ago I saked him if he would allow me to use the followin cartoon like an avatar in the spanish forum, and he said taht it was for ok for hom. With this one I do not know

DSCI0080.JPG (233.43 KiB) Viewed 24143 times

ciao norbert

https://www.youtube.com/watch?v=M4tlDUld0NI

https://www.youtube.com/watch?v=WRoafXOb3yE

https://www.youtube.com/watch?v=e6sRNkOfs1s

[Ming]

You'd need to look here I think.
http://www.joebarteam.ventsdouest.com

Oops, must check for the signature in future!
Both excellent representations though, I think.
Bob.

[Jaydub]

Not been on here for a while... just read the whole thread.
Is this all okay now if you've had the chance to, hopefully, put a few miles on it? For your sake I hope so - have had similar problems on my old stuff and the frustration can get to you after a bit...